Is it permissible to divorce a sick wife who does not meet sexual needs, given the presence of children and the financial inability to marry another?

Allah has permitted polygyny for many reasons, among them that the wife may be ill and unable to fulfill her husband's needs. In such a case, the husband should not remain deprived or divorce the mother of his children; instead, he should marry another woman. If the husband is financially unable to practice polygyny, it is not permissible for him to proceed with it. However, if his only options are to divorce or to marry another despite his financial inability, then he should seek his wife's permission and ask her to waive some of her rights (such as housing and maintenance for the second wife). He should also explain his situation to the second prospective wife. If she accepts, then it is permissible for him to marry her. In the event that the wife does not agree to waive her rights, he may divorce her if he fears falling into what Allah has forbidden.